With high development of economy, municipal solid wastes (MSW) are increasing quickly, especially industry hazardous wastes, medical wastes etc., which, if were not properly handled, will become a big direct threaten to human life. During recent years, MSW were increasing largely, at an annual growth rate of 8%, and until now in China, wastes amounts are over 150 million tons. Therefore, how to treat such a mass of wastes has been paid attention more and more. Presently, waste combustion method is the most effective method to solve wastes problem. Incineration method can alleviate pressure of MSW disposal and plough, but, at the mean time, many problems occasioned. Such as acid gases in exhaust ash may bring high or low temperature erosion to heat transfer surface and flue. In addition, dioxin in flue gases, which is noxious and carcinogenic, if are not properly treated, serious secondary pollution will be triggered.
Waste incinerator has been widely used in waste combustion system. However, toxic substances in flue gases generated from waste combustion process are increased accordingly, especially toxic gases from combustion of medical wastes, industry wastes et cetera. Meanwhile, since waste gas emission standard is very strict all over the world, which will be stricter in the future, so higher requests for flue gases purification technology are needed. Strict emission standard often greatly enlarges invest and operation cost of purification system.
Majority pollutants from incinerator are variation of acid gases, chlorides, SO2, CO, heavy metals, dust, dioxin and so on, furthermore tar content in these exhaust gas is rather high. And the existing status of these pollutants including gaseous, liquid and solid forms. Some of the polluters can be decreased by incineration process upgrade. But most are to be improved in the flue gases purification technology and system process design.
Polluters contained in the flue ash are as below:
PollutantAmount (mg/Nm3)Dust1000-20000HCl100-3300SOX200-3900HF   5.8NOX750Hg0.2-5.0 CO300Other Heavy Mentals5-30Total Organics200-2000
It can be seen that flue ash from incinerator contains large quantities of harmful gases. The kinds of polluter gases are greatly depended on waste content and auxiliary fuel. So there are many limited items for incinerator flow ash emission domestic and foreign, and the emission criterion is stricter than industry. As the late start step of incineration technology and lag in flue ash purification technology in our country, usually easy to lead to second pollution. There are still many problems in the present application.
At present, all technology and patent already existed cannot solve the difficulties flue ash purification technology faced. Many of the technology dispelling acid gas and dioxin adopt shock chilling, alkali spraying or phase carbon absorption system. But they have the disadvantage of high cost, complex dispose equipment, non-complete dispose and serious second pollution. CN101178181 adopts shock chilling to make temperature of flow ash low to 155˜188° C. from high degree in seconds, then use alkali spraying technology. This method leads to high waste of energy, big consumption of water and enlarge the disposal cost. CN101099921 use carbon absorption system to absorb dioxin. But by this way it cannot stop the formation of dioxin radically and disposal cost are extremely high. Hydro-thermal treatment is applied to disposal incineration ash in CN101050862, in which dioxin and other harmful gas can be eliminated, however, it generates waste water and waste water treatment have to be added. As a result, large water resource will be cost.
Therefore, in this field, a method and related system is urgently needed which could eliminate the environment pollution brought by waste incineration especially pollution brought by the flue ash from incinerator process progress. The system is also needed to completely dispose all the harmful acid gas, dioxin and dioxin precursors.